Degree Type


Date of Award


Degree Name

Doctor of Philosophy


Food Science and Human Nutrition


Nutritional Sciences

First Advisor

Donald C. Beitz

Second Advisor

Stephanie Clark


It is an often overlooked, but vital, research question to understand how what is fed to food-producing animals ultimately affects quality and consumer acceptability of food products produced by those animals. Of interest in recent years, particularly in the Midwest, has been the effect of inclusion of dried distillers grains with solubles (DDGS) in the rations of lactating dairy cows on milk and cheese quality. Because of the high unsaturated oil content of DDGS, feeding DDGS to dairy cows could potentially lead to decreased oxidative stability of milk and cheese and also contribute to the late blowing of eyes in Swiss type cheeses. Therefore, it was of interest to investigate if feeding full-fat DDGS (~13 % fat) would result in increased development of off-flavors in milk and could result in milk that was unsuitable for use in baby Swiss cheese production. Additionally, the recent development of reduced-fat DDGS (RF-DDGS) (~6% fat) offers the possibility of feeding increased amounts of DDGS, compared to feeding full-fat DDGS, without adversely affecting milk and milk fat production. Because of the possibility of higher rates of inclusion of RF- DDGS in the rations of dairy cows than was possible with full-fat DDGS, it was necessary to investigate the effects of feeding RF-DDGS on milk production efficiency and the quality of milk for the production of baby Swiss cheese. Finally, feedstuffs containing high concentrations of unsaturated fatty acids, in particular DDGS, can adversely affect the quality of pork fat, potentially resulting in pork that is unacceptable to the producer and consumer. Specific project summaries are described in the subsequent pages.

Quality of Milk from Lactating Dairy Cattle Fed Dried Distillers Grains with Solubles

The objective of this study was to examine the effect of feeding DDGS to healthy mid-lactation Holstein dairy cows (n=24) on production parameters and flavor and oxidative stability of milk. Cows were assigned to two groups and fed one of three treatment diets (0% DDGS, 10% DDGS, 25% DDGS by dry matter (DM)) as an isocaloric total mixed ration. Each group was fed all three diets after a wash-out period of 7 days. Milk yield was unaffected by both the 0% and 10% DDGS diets but decreased significantly when fed the 25% DDGS diet. The quality of milk from cows fed DDGS was characterized through chemical analyses profiling fatty acids and analyzing milk composition. Rumen volatile fatty acids were unaffected by treatment. Milk protein and solids-not-fat (SNF) increased with increasing inclusion of DDGS, but milk fat decreased concomitantly. Milk fatty acid composition, on a weight percent basis, was significantly affected; cows fed higher concentrations of DDGS produced milk with higher concentrations of unsaturated fatty acids. An assessment of milk quality by a trained sensory panel showed no effect of dietary treatment on milk oxidative stability or milk flavor. The results of this study indicate that feeding of DDGS to lactating dairy cows, under controlled conditions, does not negatively affect milk oxidative stability or flavor; feeding 25% DDGS, however, did negatively impact milk production and changed the milk fatty acid profile.

Lactational Performance of Lactating Holstein Dairy Cows Fed Full-Fat and Reduced-Fat Dried Distillers Grains with Solubles

Our objective was to evaluate production performance of lactating Holstein dairy cows fed two different dietary concentrations of full-fat DDGS (13.6% fat). Thirty cows were fed 0, 10, and 20% DDGS (DM basis) as a total mixed ration (TMR) in a 3 × 3 crossover. Cows were stratified into groups of 10 by parity and days in milk and fed each of three diets in three 28-day periods. Based on previous research, we hypothesized that feeding 20% DDGS (DM basis) would negatively influence production and feed efficiency of dairy cattle. Milk yield was decreased significantly when fed 20% DDGS, and feeding DDGS caused milk fat depression and decreased daily fat yield, resulting in significant decreases in 3.5% fat-corrected milk (FCM) yield and energy-corrected milk (ECM) yield. Both protein and lactose percentages increased significantly when cows were fed 20% DDGS; neither protein nor lactose yield, however, was significantly affected. Protein efficiency, a measure of the utilization of dietary protein for milk protein synthesis, decreased significantly for cows fed 20% DDGS, likely resulting from heat-damaged protein, as indicated by proximate analyses. All three measures of energetic efficiency (ECM/DMI, kg ECM/net energy for lactation (NEL) intake (Mcal) and gross energy of milk produced (Mcal)/NEL caloric intake (Mcal)) were significantly decreased when cows were fed 20% DDGS but not when cows were fed 10% DDGS. These results indicate that, with the exception of an approximate loss of milk fat of 0.5% percentage points, full-fat DDGS used in this study can be effectively fed at 10% without a loss in production performance when compared with a traditional TMR. Feeding the full-fat DDGS at 20%, however, is not advisable.

In contrast with results from feeding FF-DDGS, negative effects of feeding RF-DDGS to lactating dairy cows did not occur when 36 multiparous and mid lactation Holstein dairy cows were fed either 0 or 20% reduced-fat DDGS (RF-DDGS) in a 2 × 2 crossover design. Cows were assigned randomly to treatment groups and were fed individually to allow for collection of feed intake data. Feeding RF-DDGS as 20% DM of a TMR supplemented with rumen-protected lysine did not negatively influence production parameters related to milk composition or nutritional physiology of the cow. Milk urea nitrogen (MUN) was, however, decreased, and milk protein percentage was increased. Total milk solids concentration were not influenced by inclusion of RF-DDGS. Additionally, RF-DDGS did cause a decrease in FCM efficiency as a result of an increase in DMI. When ECM efficiency was calculated (accounting for fat, protein, and lactose concentration in milk), no difference in feed efficiency resulted.

These data indicate that RF-DDGS can be included effectively in rations of multiparous lactating dairy cows, at least when supplemented with lysine. Additionally, decreased MUN and increased milk protein percentage indicate that dietary protein utilization may be improved by including RF-DDGS as a protein source in the ration, presumably because DDGS are generally considered to be a good source of rumen undegradable protein. Taken together, these results indicate that RF-DDGS may be an attractive feed ingredient for 20% inclusion in lactating ruminant diet.

Reduced-Fat Dried Distillers Grains with Solubles Did Not Reduce Quality of Baby Swiss Cheese

Thirty-six multiparous and mid lactation Holstein dairy cows were fed either 0 or 20% reduced-fat DDGS (RF-DDGS) in a 2 × 2 crossover design. Cheeses were produced a total of six times from each treatment. In this experiment, feeding RF-DDGS as 20% DM of a total mixed ration (TMR) supplemented with lysine did not negatively influence flavor attributes of baby Swiss cheese. Eye appearance in all cheeses was atypical but was not related to diet. Any defects in appearance of Baby Swiss cheese appeared in both control and RF-DDGS fed cows. The results indicate that lactating Holstein dairy cows can be fed RF-DDGS as 20% DM of a TMR without negatively affecting usability of milk, when compared with control, for production of Baby Swiss cheese.

Relationship of Fat Quality and Meat Quality Traits of Fresh Pork

Feeding distillers grains to pigs can lead to undesirable traits in meat quality that adversely affect both consumer acceptability and the ability of the processor to produce high quality pork products. Additionally, interest has been expressed by both processors and the research community about how fat quality varies among anatomical locations.

Barrows and gilts (n=347) of five purebred lines and one commercial crossbred line were fed commercial swine diets with FF-DDGS inclusion at 30% of DM. For the final 30 days of feeding, DDGS were removed from the diet. Pigs were harvested at a minimal weight of 111.4 kg. At harvest, fat was collected from the back, belly, and jowl, and meat samples were taken from the longissimus muscle for evaluation of fat and meat quality characteristics. Jowl fat iodine values were significant predictors of back and belly fat iodine values, and increases in iodine value of the fat of the pork chop were moderately and negatively correlated with several measures of meat quality. This study demonstrates that iodine value of fat from one anatomical location (i.e., back and belly) is related to iodine value of a less valuable anatomical location (i.e., jowl); additionally, increases in iodine value correlate negatively with predictors of meat quality.


Copyright Owner

Eric David Testroet



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200 pages